Catheter having closed electrode assembly with spines of uniform length

ABSTRACT

A catheter comprising an elongated catheter body, and an electrode assembly distal of the catheter body, the assembly comprising a plurality of spines, wherein each spine has a distal end that is connected to the distal end of at least one other spine, wherein each spine has an electrode-carrying portion, the electrode-carrying portions of all spines of the assembly being in a single common plane, and wherein all spines of the assembly have a uniform exposed total length.

FIELD OF INVENTION

This invention relates to catheters, in particular, intravascularcatheters for tissue diagnostics and ablation.

BACKGROUND

Cardiac arrhythmia, such as atrial fibrillation, occurs when regions ofcardiac tissue abnormally conduct electric signals to adjacent tissue,thereby disrupting the normal cardiac cycle and causing asynchronousrhythm. Important sources of undesired signals are located in the tissueregion, for example, one of the atria or one of the ventricles.Regardless of the sources, unwanted signals are conducted elsewherethrough heart tissue where they can initiate or continue arrhythmia.

Procedures for treating arrhythmia include surgically disrupting theorigin of the signals causing the arrhythmia, as well as disrupting theconducting pathway for such signals. More recently, it has been foundthat by mapping the electrical properties of the endocardium and theheart volume, and selectively ablating cardiac tissue by application ofenergy, it is possible to cease or modify the propagation of unwantedelectrical signals from one portion of the heart to another. Theablation process destroys the unwanted electrical pathways by formationof non-conducting lesions.

In this two-step procedure—mapping followed by ablation—electricalactivity at points in the heart is typically sensed and measured byadvancing a catheter containing one or more electrical sensors into theheart, and acquiring data at a multiplicity of points. These data arethen utilized to select the target areas at which ablation is to beperformed.

For greater mapping resolution, it is desirable for a mapping catheterto provide very high density signal maps through the use of a multitudeof electrodes sensing electrical activity within a small area, forexample, about a square centimeter. For mapping within an atria or aventricle (for example, an apex of a ventricle), it is desirable for anelectrode assembly to collect larger amounts of data signals withinshorter time spans. It is also desirable for such an electrode assemblyto be adaptable to different tissue surfaces, for example, flat, curved,irregular or nonplanar surface tissue, yet remain in a predeterminedconfiguration where electrode spatial relationships are generallymaintained during sensing and mapping. With more complex electrodegeometries, it is further desirable that the electrode assembly bereadily collapsible to be advanced through a guiding sheath.

SUMMARY OF THE INVENTION

The present invention includes a catheter having a distal electrodeassembly or array that is readily collapsible despite a complicatedgeometry. In some embodiments, the catheter of the present inventionincludes an elongated catheter body, and an electrode assembly distal ofthe catheter body, the assembly comprising a plurality of spines,wherein each spine has a distal end that is connected to the distal endof at least one other spine, wherein each spine has anelectrode-carrying portion, the electrode-carrying portions of allspines of the assembly being in a single common plane, and wherein allspines of the assembly have a uniform exposed total length.

In more detailed embodiments, the electrode-carrying portions arelinear, wherein the electrode-carrying portions may be parallel witheach other.

In more detailed embodiments, the electrode-carrying portions areparallel with a longitudinal axis of the catheter.

In more detailed embodiments, t the array has longitudinal symmetry,wherein each spine may have a counterpart spine.

In more detailed embodiments, each spine has at least a divergentproximal portion and/or each spine has at least a convergent distalportion.

In more detailed embodiments, at least one spine has a divergentproximal portion and a convergent proximal portion that is distal of thedivergent proximal portion.

In more detailed embodiments, at least one spine has a convergent distalportion and a divergent distal portion that is proximal of theconvergent distal portion.

In more detailed embodiments, the plurality of spines ranges betweenabout two and eight, and more preferably between about three and six.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of a catheter of the present invention, inaccordance with some embodiments.

FIG. 2A is a side cross-sectional view of the catheter of FIG. 1,including a junction between a catheter body and a deflection section,taken along a first diameter.

FIG. 2B is a side cross-sectional view of the catheter of FIG. 1,including the junction of FIG. 2A, taken along a second diametergenerally perpendicular to the first diameter.

FIG. 2C is an end cross-sectional view of the deflection section ofFIGS. 2A and 2B, taken along line C-C.

FIG. 3A is a side cross-sectional view of the catheter of FIG. 1,including a junction between the deflection section and a distalelectrode assembly, taken along a first diameter.

FIG. 3B is a side cross-sectional view of the junction of FIG. 3A, takenalong a second diameter generally perpendicular to the first diameter.

FIG. 3C is an end cross-sectional view of the deflection section ofFIGS. 3A and 3B, taken along line C-C.

FIG. 3D is an end cross-sectional view of the junction of FIG. 3A, takenalong line D-D.

FIG. 4 is a perspective view of a junction between the deflectionsection and the distal electrode assembly, with parts broken away.

FIG. 5A is a perspective view of a distal electrode assembly of FIG. 1.

FIG. 5B is an end cross-sectional view of a ring electrode mounted on aspine of FIG. 5A, taken along line B-B.

FIG. 5C is a perspective view of spine supports and mounting stem of thedistal electrode assembly of FIG. 5A.

FIG. 5D is a side view of the spine supports and mounting stem of FIG.5C.

FIG. 5E is a top view of two spines of an electrode array, in accordancewith one embodiment of the present invention.

FIG. 6A is a perspective view of an irrigated ring electrode mounted ona spine, in accordance with one embodiment.

FIG. 6B is a side cross-sectional view of the irrigated ring electrodeof FIG. 6A, taken along line A-A.

FIG. 6C is an end cross-sectional view of the irrigated ring electrodeof FIG. 6B, taken along line B-B.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, the catheter 10 comprises an elongated catheter body12, an intermediate deflection section 14, a distal electrode assemblyor array 15 with a plurality of spines 25, and a deflection controlhandle 16 attached to the proximal end of the catheter body 12. Inaccordance with a feature of the present invention, the distal electrodearray 15 includes multiple spine supports that enable the spines to bemounted to the distal end of the catheter in a spatially efficientmanner that accommodates more complex spine geometries while improvingelectrode-to-tissue contact and improves manufacturability of thecatheter.

With reference to FIGS. 2A and 2B, the catheter body 12 comprises anelongated tubular construction having a single, axial or central lumen18. The catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. In someembodiments, the catheter body 12 comprises an outer wall 20 made ofpolyurethane or PEBAX. The outer wall 20 comprises an imbedded braidedmesh of stainless steel or the like to increase torsional stiffness ofthe catheter body 12 so that, when the control handle 16 is rotated, theintermediate section 14 of the catheter 10 rotates in a correspondingmanner.

The outer diameter of the catheter body 12 is not critical. Likewise,the thickness of the outer wall 20 is not critical, but is thin enoughso that the central lumen 18 can accommodate a puller wire, one or morelead wires, and any other desired wires, cables or tubes. If desired,the inner surface of the outer wall 20 is lined with a stiffening tube22 to provide improved torsional stability.

As shown in FIGS. 2A, 2B and 2C, the intermediate section 14 comprises ashorter section of tubing 19 having multiple lumens, for example, fouroff-axis lumens 31, 32, 33 and 34. The first lumen 31 carries aplurality of lead wires 40S for ring electrodes 37 mounted on the array15. The second lumen 32 carries a first puller wire 24. The third lumen33 carries a cable 36 for an electromagnetic position sensor 42 and aplurality of lead wires 40D and 40P for distal and proximal ringelectrodes 38D and 38P carried on the catheter proximally of the distalelectrode array 15. The fourth lumen 34 (for example, diametricallyopposite of the second lumen 32 in the illustrated embodiment) carries asecond puller wire 26. The tubing 19 is made of a suitable non-toxicmaterial that is preferably more flexible than the catheter body 12. Onesuitable material for the tubing 19 is braided polyurethane, i.e.,polyurethane with an embedded mesh of braided stainless steel or thelike. The size of each lumen is not critical, but is sufficient to housethe lead wires, puller wires, the cable and any other components.

The useful length of the catheter, i.e., that portion that can beinserted into the body excluding the distal electrode array 15, can varyas desired. Preferably the useful length ranges from about 110 cm toabout 120 cm. The length of the intermediate section 14 is a relativelysmaller portion of the useful length, and preferably ranges from about3.5 cm to about 10 cm, more preferably from about 5 cm to about 6.5 cm.

A means for attaching the catheter body 12 to the intermediate section14 is illustrated in FIGS. 2A and 2B. The proximal end of theintermediate section 14 comprises an outer circumferential notch 27 thatreceives the inner surface of the catheter body 12. The intermediatesection 14 and catheter body 12 are attached by glue or the like.

If desired, a spacer (not shown) can be located within the catheter bodybetween the distal end of the stiffening tube (if provided) and theproximal end of the intermediate section. The spacer provides atransition in flexibility at the junction of the catheter body andintermediate section, which allows this junction to bend smoothlywithout folding or kinking. A catheter having such a spacer is describedin U.S. Pat. No. 5,964,757, the disclosure of which is incorporatedherein by reference.

As shown in FIGS. 3A and 3B, the distal electrode array 15 includes amounting member or stem 46 in the form of a short tubing mounted on adistal end of the tubing 19 of the intermediate section 14. It isunderstood that the stem may be mounted onto the distal end of thecatheter body 12 where the catheter includes no deflection section. Thestem 46 has a central lumen 48 to house various components. Theintermediate section 14 and stem 46 are attached by glue or the like.The stem 46 may be constructed of any suitable material, includingnitinol.

As shown in FIG. 4, the stem 46 houses various components, including,for example, the electromagnetic position sensor 42, and a distal anchorfor the puller wires 24 and 26. In the disclosed embodiment, the distalanchor includes one or more washers, for example, a distal washer 50Dand a proximal washer 50P, each of which has a plurality of matchingaxial through-holes that allow passage of components between thedeflection section 14 and the stem 46 while maintaining axial alignmentof these components relative to the longitudinal axis 95 of the catheter10. As shown in FIGS. 3D and 4, the through-holes include holes 54 and56 that are axially aligned with the second and fourth lumens 32 and 34of the tubing 19, respectively, to receive a distal end of puller wires24 and 26, respectively. It is understood that the puller wires 24 and26 may actually form a single tensile member with a distal U-bendsection that passes through the holes 54 and 56. With tension on thewashers 50D and 50P exerted by the U-bend section of the puller wires 24and 26, the washers firmly and fixedly abut against the distal end ofthe tubing 19 of the deflection section 14 to distally anchor the U-bendsection.

As shown in FIGS. 3D and 4, each washer also includes through-hole 58which is axially aligned with the first lumen 31 and allows passage ofthe lead wires 40S from the deflection section 14 and into the lumen 48of the stem 46. Each washer further includes through-hole 57 which isaxially aligned with the third lumen 33 and allows passage of the sensorcable 36 from the deflection section 14 into lumen 48 of the stem 46where the electromagnetic position sensor 42 is housed. The lead wire40D also passes through the hole 57 to enter the lumen 48 for attachmentto the distal ring electrode 38D carried on the outer surface of thestem 46 via an opening (not shown) formed in the side wall of the stem46 through which a distal end of the lead wire 40D is welded orotherwise attached to the distal ring electrode 38D, as known in theart. Carried on the outer surface of the tubing 19 near the distal endof the intermediate deflection section 14, a proximal ring electrode 38Pis connected to lead wire 40P via an opening 87 (FIG. 3B) formed in theside wall of the tubing 19 that provides communication between the thirdlumen 33 and outside of the tubing 19. The distal end of the lead wireis welded or otherwise attached to the proximal ring electrode 38P asknown in the art.

The distal electrode array 15 extends from a distal end of the tubing 19of the deflection section 14 (or a distal end of the catheter body 12where the catheter is without a deflection section). As shown in theembodiment of FIG. 5A, the array 15 includes a plurality of elongatedspines 25, each of whose distal end 25T is joined to a distal end 25T ofat least another spine 25. Accordingly, the array 15 has a closedconfiguration in that the array is without any spine whose distal end isfree and unconnected to another spine. In some embodiments, each spine25 of the array 15 has at least one proximal portion 25PD that isdivergent from a longitudinal axis 95 and at least one distal portion25DC that is convergent toward the longitudinal axis 95. The array 15also includes selected spines with at least one proximal portion 25PCthat is convergent toward the longitudinal axis 95 that is distal of thedivergent proximal portion 25PD, and at least one distal portion 25DDthat is divergent from the longitudinal axis 95 that is proximal of theconvergent distal portion 25DC. The plurality of spines may rangebetween about two and eight, more preferably, between about four andsix.

In some embodiments, the array 15 is longitudinally symmetrical in thateach spine 25 has an opposing mirror counterpart across the longitudinalaxis 95, with which its distal end 25T is connected to the distal end25T of its counterpart.

In some embodiments, each spine has an electrode-carrying portion distalof the proximal portion 25PD on which one or more ring electrodes 37 aremounted. In some embodiments, the plurality of ring electrodes 37 perspine may range between about 6 and 12, preferably about 6 and 9, andmore preferably about 8. In some embodiments, these electrode-carryingportions are linear, extending parallel with each other and/or with thelongitudinal axis 95. In some embodiments, these electrode-carryingportions are also all lying in a single common plane, even where theproximal portions 25PD are not lying in the single common plane. In someembodiments, these electrode-carrying portions are uniformly separatedlaterally by a predetermined distance.

Each spine 25 includes a shape-memory member 26 and a surroundingnonconductive tubing or covering 64. The covering 64 has a central lumen65 through which the shape-memory 26 extends along with lead wires 40Sfor ring electrodes 37, as shown in FIG. 5B. The covering 64 extends thelength of the exposed portion of spine 25, from distal of the stem 46 tothe distal tip end of the spine.

In some embodiments, a total exposed length of each spine of the array15 is equal or uniform. For example, as shown in FIG. 5E, spines X and Yof an array have equal total exposed lengths X_(T) and Y_(T), whereX_(T)=Y_(T), each defined as follows. Notably, lengths X5 and Y8 areexposed lengths, measured distal of the stem 46 to exclude any portionextending inside the stem 46.X _(T) =X1+X2+X3+X4+X5  (Eqn. 1)Y _(T) =Y1+Y2+Y3+Y4+Y5+Y6+Y7+Y8  (Eqn. 2)

Advantageously, an array with spines having equal exposed total lengthsreadily collapses into an elongated arrangement that can be more easilyfed through a guiding sheath. The longitudinal symmetry of the arrayalso facilitates the array collapsing into an elongated arrangement.

In some embodiments, the shape-memory supports 26 and the stem 46 aremade of a material having shape-memory, i.e., that can be temporarilystraightened or bent out of its original shape upon exertion of a forceand is capable of substantially returning to its original shape in theabsence or removal of the force. One suitable material for the supportmember is a nickel/titanium alloy. Such alloys typically comprise about55% nickel and 45% titanium, but may comprise from about 54% to about57% nickel with the balance being titanium. A nickel/titanium alloy isnitinol, which has excellent shape memory, together with ductility,strength, corrosion resistance, electrical resistivity and temperaturestability. The spine supports may be formed from a sheet material whichis, for example, die cut or laser cut into the configuration of the baseand the spines. The non-conductive covering 64 can be made of anysuitable material, and is preferably made of a biocompatible plasticsuch, as polyurethane or PEBAX.

At the junction of distal electrode array 15 and the stem 46, thenon-conductive covering 64 of each spine 25 may be attached and sealedat its proximal end to the stem 46 by polyurethane or the like.

For each spine 25, one or more ring electrodes 37 are mounted over thecovering 64. Proximal of the array 15, the lead wires 40S for the ringelectrodes 37 extend through a protective polytube 68. The lead wires40S diverge near the distal end of the polytube 68, and extend towardtheir respective spine 25, into the lumen 65 of the respectivenonconductive covering 64. As shown in FIG. 5B, each lead wire 40S isconnected to its respective ring electrode 37 via a respective opening69 formed in the side wall of the covering 64 through which a distal endof the lead wire reaches outside of the covering 64 and is welded orotherwise attached to its ring electrode 37.

In other embodiments, irrigated ring electrodes 37I are carried on thespines 25, as shown in FIGS. 6A, 6B and 6C. The spines 25 is covered bya multi-lumened tubing 80 having, for example, a first lumen 81 for theshape-memory member 26, a second lumen 82 for lead wires 40S, and athird lumen 83 for passing irrigation fluid via a passage 88 formed inthe sidewall of the tubing 80 to annular space gap G between outer wallof the tubing 80 and side wall of the ring electrode 37I which areformed with fluid ports 85.

The proximal ends of the lead wires 40S, 40D and 40P for the spine loopring electrodes 37, and for the distal and proximal ring electrodes 38Dand 38P, respectively, are electrically connected to a suitableconnector (not shown) in the distal end of the control handle 16, whichis connected to a source of ablation energy, e.g., RF energy, as isknown in the art. The lead wires 40S, 40D and 40P extend through thecentral lumen 18 of the catheter body 12 (FIG. 2B). The lead wires 40Sextend through the first lumen 31 of the tubing 19 of the intermediatesection 14, and the lead wires 40D and 40P extend through the thirdlumen 33 of the tubing 19 (FIGS. 2C and 3C). Passing through the holes58 in the washers 50D and 50P, the lead wires 40S extend through thepolytube 68 which protects them from being damaged by the hole 58 (FIG.3D).

In the depicted embodiment, the lead wires 40S extending through thecentral lumen 18 of the catheter body 12 and the first lumen 31 in thedeflection section 14 may be enclosed within a protective sheath 94 toprevent contact with other components in the catheter. The protectivesheath can be made of any suitable material, preferably polyimide. Aswould be recognized by one skilled in the art, the protective sheath canbe eliminated if desired.

The ring electrodes 37, 37I and 38D and 38P are made of any suitablesolid conductive material, such as platinum or gold, preferably acombination of platinum and iridium, and mounted onto the non-conductivecover 64 and the stem 46 with glue or the like. Alternatively, the ringelectrodes can be formed by coating the non-conductive cover 64 and stem46 with an electrically conducting material, like platinum, gold and/oriridium. The coating can be applied using sputtering, ion beamdeposition or an equivalent technique.

In some embodiments, each ring electrode 37 carried on the spines 25 isrelatively short, having a length ranging from about 0.4 mm to about0.75 mm. Moreover, the electrodes may be arranged in pairs, where twoelectrodes of a pair are spaced more closely to each other than they areto other pairs of electrodes. The closely-spaced electrode pairs allowfor more accurate detection of near field pulmonary vein potentialversus far field atrial signals, which is very useful when trying totreat atrial fibrillation. Specifically, the near field pulmonary veinpotentials are very small signals whereas the atria, located very closeto the pulmonary vein, provides much larger signals. Accordingly, evenwhen the mapping array is placed in the region of a pulmonary vein, itcan be difficult for the physician to determine whether the signal is asmall, close potential (from the pulmonary vein) or a larger, fartherpotential (from the atria). Closely-spaced bipole electrodes permit thephysician to more accurately determine whether he is looking at a closesignal or a far signal. Accordingly, by having closely-spacedelectrodes, one is able to target exactly the locations of myocardialtissue that have pulmonary vein potentials and therefore allows theclinician to deliver therapy to the specific tissue. Moreover, theclosely-spaced electrodes allow the physician to determine the exactanatomical location of the ostium/ostia by the electrical signal.

In some embodiments, a proximal electromagnetic position sensor 42 ishoused in the lumen of the stem (FIG. 4). A sensor cable 36 extends froma proximal end of the position sensor 42, and through the hole 57 of thewashers 50 (FIG. 3D), the third lumen 33 of the tubing 19 of thedeflection section 14 (FIG. 2C), and the central lumen 18 of thecatheter body 12 (FIG. 2B). The cable 36 is attached to a PC board inthe control handle 16, as known in the art. In some embodiments, one ormore distal electromagnetic position sensors may be housed in the array,for example, in one or more distal portions of the array. Sensor cables36D may extend through the lumen 65 of spine covering 64 (FIG. 5B) or afourth lumen 84 of the tubing 80 (FIG. 6B).

As shown in FIGS. 2A and 2C, the puller wires 24 and 26 (whether as twoseparate tensile members or parts of a single tensile member) areprovided for bi-directional deflection of the intermediate section 14.The puller wires 24 and 26 are actuated by mechanisms in the controlhandle 16 that are responsive to a thumb control knob or a deflectioncontrol knob 11. Suitable control handles are disclosed in U.S. Pat.Nos. 6,123,699; 6,171,277; 6,183,435; 6,183,463; 6,198,974; 6,210,407and 6,267,746, the entire disclosures of which are incorporated hereinby reference.

The puller wires 24 and 26 extend through the central lumen 18 of thecatheter body 12 (FIG. 2A) and through the second and fourth lumens 32and 34, respectively, of the tubing 19 of the deflection section 14(FIG. 2C). As shown in FIGS. 3A and 3C, they extend through holes 54 and56, respectively of the washers 50. Where the puller wires are part of asingle tensile member, the single tensile member has a U-bend 24/26U(FIG. 3A) at the distal face of the distal washer 50D which anchors thedistal ends of the puller wires. In that regard, the U-bend extendsthrough a short protective tubing 70 to protect the puller wires fromthe holes 54 and 56. Alternatively, where the puller wires are separatetensile members, their distal ends may be anchored via T-bars, as knownin the art and described in, for example, U.S. Pat. No. 8,603,069, theentire content of which is incorporated herein by reference. In anycase, the puller wires 24 and 26 are made of any suitable metal, such asstainless steel or Nitinol, and each is preferably coated with TEFLON orthe like. The coating imparts lubricity to the puller wires. The pullerwires preferably have a diameter ranging from about 0.006 to about 0.010inch.

A compression coil 66 is situated within the central lumen 18 of thecatheter body 12 in surrounding relation to each puller wire 24, asshown in FIG. 2B. Each compression coil 66 extends from the proximal endof the catheter body 12 to the proximal end of the intermediate section14. The compression coils 66 are made of any suitable metal, preferablystainless steel. Each compression coil 66 is tightly wound on itself toprovide flexibility, i.e., bending, but to resist compression. The innerdiameter of the compression coil 66 is preferably slightly larger thanthe diameter of its puller wire. The Teflon coating on each puller wireallows it to slide freely within its compression coil.

The compression coil 66 is anchored at its proximal end to the outerwall 20 of the catheter body 12 by a proximal glue joint (not shown) andat its distal end to the intermediate section 14 by a distal glue joint92. Both glue joints may comprise polyurethane glue or the like. Theglue may be applied by means of a syringe or the like through a holemade the sidewalls of the catheter body 12 and the tubing 19. Such ahole may be formed, for example, by a needle or the like that puncturesthe sidewalls which are heated sufficiently to form a permanent hole.The glue is then introduced through the hole to the outer surface of thecompression coil 66 and wicks around the outer circumference to form aglue joint about the entire circumference of the compression coil.

Within the second and fourth lumens 32 and 34 of the intermediatesection 14, each puller wire 24 and 26 extends through a plastic,preferably Teflon, puller wire sheath 39 (FIGS. 2A and 2C), whichprevents the puller wires from cutting into the wall of the tubing 19 ofthe deflection section 14 when the deflection section 14 is deflected.

In some embodiments, the ring electrodes 38D and 38P proximal of thearray 15 serve as reference electrodes for visualization of the catheteron a 3-D mapping system, such as CARTO® 3 SYSTEM available from BiosenseWebster, Inc., which automatically locates the EM sensor 42, processesreference location values from electrodes 38D and 38P, which are at aconstant location from the EM sensor(s) and determines the location ofthe electrodes 37 and 37I and visualizes the remainder of the electrodearray 15.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. As understood by one of ordinary skill in the art, thedrawings are not necessarily to scale. Also, different features ofdifferent embodiments may be combined as needed or appropriate.Moreover, the catheters described herein may be configured to applyvarious energy forms, including microwave, laser, RF and/or cryogens.Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

What is claimed is:
 1. A catheter comprising: an elongated catheterbody; and an electrode assembly distal of the catheter body, theassembly comprising a plurality of spines, wherein the plurality ofspines includes at least three spines, wherein each spine has a distalend that is connected to the distal end of at least one other spine,wherein each spine has an electrode-carrying portion, theelectrode-carrying portions of all spines of the assembly being in asingle common plane, wherein all spines of the assembly have a uniformexposed total length, wherein the electrode-carrying portions arelinear, and wherein the electrode-carrying portions are parallel with alongitudinal axis of the catheter.
 2. The catheter of claim 1, whereinthe electrode-carrying portions are parallel with each other.
 3. Thecatheter of claim 1, wherein the assembly has longitudinal symmetry. 4.The catheter of claim 1, wherein each spine has a mirror counterpartspine.
 5. The catheter of claim 1, wherein each spine has anonconductive covering.
 6. The catheter of claim 1, wherein each spinehas at least one ring electrode.
 7. The catheter of claim 1, whereineach spine has at least one irrigated ring electrode.
 8. The catheter ofclaim 1, wherein the plurality of spines includes less than eightspines.
 9. The catheter of claim 1, wherein the plurality of spinesincludes less than six spines.
 10. A catheter comprising: an elongatedcatheter body; and an electrode assembly distal of the catheter body,the assembly comprising a plurality of spines, wherein the plurality ofspines includes at least three spines, wherein each spine has a distalend that is connected to the distal end of at least one other spine,wherein each spine has an electrode-carrying portion, theelectrode-carrying portions of all spines of the assembly being in asingle common plane, wherein all spines of the assembly have a uniformexposed total length, and wherein each spine has at least a divergentproximal portion.
 11. The catheter of claim 10, wherein at least onespine has a convergent proximal portion that is distal of the divergentproximal portion.
 12. A catheter comprising: an elongated catheter body;and an electrode assembly distal of the catheter body, the assemblycomprising a plurality of spines, wherein the plurality of spinesincludes at least three spines, wherein each spine has a distal end thatis connected to the distal end of at least one other spine, wherein eachspine has an electrode-carrying portion, the electrode-carrying portionsof all spines of the assembly being in a single common plane, whereinall spines of the assembly have a uniform exposed total length, andwherein each spine has at least a convergent distal portion.
 13. Thecatheter of claim 12, wherein at least one spine has a divergent distalportion that is proximal of the convergent distal portion.